Whether in large-scale industrial pipelines or in everyday applications such as ship pipelines and automobile pipelines, the clever connection of various pipe bends is indispensable. Pipe bends not only change the direction of pipelines but, through their unique design and processing technology, also ensure smooth fluid flow and efficient system operation.
However, despite the importance of pipe bends in pipeline systems, many people know very little about their processing techniques, classifications, and maintenance. Many may only be aware of the existence of pipe bends but are unclear about how they are manufactured and how to select the appropriate pipe bend to meet specific application requirements.
Today, let us delve into the mysteries of pipe bends, helping everyone better understand this important component. By analyzing in detail the classification, processing technology, application scenarios, and maintenance methods of pipe bends, we will unveil the science and technology behind them, giving a more comprehensive understanding of this seemingly ordinary component.
There are many types of pipe bends, and they can be classified in various ways according to different standards.
Large Pipe Bends: These are typically used in large industrial projects, such as oil pipelines and chemical pipelines. They are large in size, able to withstand higher pressure and flow, and suitable for long-distance, high-capacity material transport.
Large-Diameter Pipe Bends: Characterized by a large diameter, these pipe bends have significant advantages when transporting large volumes of fluid. For example, in urban water supply systems, large-diameter pipe bends ensure stable water pressure and flow.
Cast Iron Pipe Bends: Cast iron pipe bends offer good corrosion resistance and stability, commonly used in drainage systems or other scenarios where corrosion resistance is crucial.
Round Pipe Bends: Round pipe bends are among the most common types. Their arc-shaped design allows fluid to flow more stably, reduces the impact on the pipe walls, and distributes forces more evenly. This design not only reduces energy loss during material transport but also extends the service life of the pipeline.
Other Shaped Pipe Bends: Besides round pipe bends, there are square, rectangular, and other special-shaped pipe bends. These are important in specific industrial applications; for instance, in certain chemical equipment, square pipe bends better accommodate the structural layout of the equipment.
The processing technology of pipe bends is diverse, with different methods suited to different application scenarios. Understanding these techniques helps in selecting suitable pipe bend products.
Hot bending is a very common processing method. The process is as follows:
Straight Pipe Cutting: First, cut the straight pipe to the required length.
Setting Guide Rings: Use a pipe bend extrusion machine to install guide rings at the bending portion of the steel pipe. The guide rings ensure the steel pipe maintains the correct direction during bending.
Heating: The induction ring heats the steel pipe with medium-frequency current until it reaches a plastic state. Temperature control is critical, as excessive heat can make the pipe brittle and prone to damage.
Bending and Cooling: Simultaneously, push the steel pipe to bend and immediately cool it after bending. Cooling is usually done with water spray to ensure the pipe bend retains its shape.
Advantages: Hot-bent pipe bends are relatively simple to process and can produce large-radius bends, suitable for arc-shaped steel structures and similar construction scenarios.
Unlike hot bending, cold bending does not rely on heating and is processed at room temperature. This method does not alter the material structure, making it suitable for applications with high material performance requirements. Cold bending is often used for small-diameter pipes, offering high processing precision but requiring advanced equipment.
Besides hot and cold bending, pipe bends can also be processed using:
Mandrel Bending: Includes cold and hot mandrel bending. Cold mandrel bending is suitable for small-diameter pipes, while hot mandrel bending is for larger diameters. Mandrel bending offers good flexibility, high pressure resistance, and low flow resistance.
Stamping: Pipe bends produced by stamping achieve high precision but are relatively costly.
Welding: Multiple pipe segments are welded together to form a bend. Welded pipe bends have high strength, but weld quality must be controlled to avoid defects.
The dimensions and parameters of a pipe bend are crucial to its performance and suitability. The following provides a detailed introduction to several key parameters.
The bending radius is an important parameter that determines the degree of curvature of the pipe bend. A larger bending radius allows the bend to be smoother, reducing fluid resistance within the pipe. Generally, the bending radius for hot-induction bends should not be less than 3.5 times the outer diameter of the pipe, while for cold-bent pipes, it should not be less than 4 times the outer diameter.
During the bending process, the wall thickness of the pipe changes. The metal on the inside of the bend is compressed, causing the wall to thicken, while the metal on the outside is stretched, causing the wall to thin. To ensure the strength and performance of the bend, it is generally stipulated that the wall thinning after bending should not exceed 15%.
Changes in the cross-sectional shape of a bend reduce the flow area, increasing fluid resistance, and also decrease the pipe’s ability to withstand internal pressure. Therefore, strict limits are set for the ovality of pipe bends: for pipe diameters ≤150 mm, ovality should not exceed 10%; for pipe diameters ≤200 mm, ovality should not exceed 8%.
Processing pipe bends requires specialized equipment, with different devices for different methods. Common equipment includes:
An electric pipe bending machine uses a motor to rotate the main shaft and bending die to bend the pipe. Key points:
Die Selection: The bending, guide, and pressing dies must match the pipe’s outer diameter to ensure quality.
Mandrel Use: For pipes over 60mm in diameter, a mandrel is inserted. The mandrel’s diameter is 1–1.5mm smaller than the pipe’s inner diameter. Correct positioning avoids wrinkles or unevenness.
Operation: Place the pipe between the bending and pressing dies along the guide die, adjust alignment, fix pipe ends with U-shaped clamps, start the motor to bend, and stop at the desired angle.
Consists mainly of a push die and pipe support, suitable for small-diameter pipes.
Die Selection: Must match the pipe’s diameter.
Operation: Place the pipe in the arc groove of the push die and support, align the center, bend to the required angle, and remove.
Notes: Avoid bending over 90° per pass; maintain proper distance between supports to prevent damage.
Uses medium-frequency induction to locally heat the pipe while mechanically rotating it, combined with water spray cooling for continuous bending. Advantages include high efficiency, small footprint, and low cost.
Preparation: Clean rust and dirt, install a suitable pipe chuck, adjust the chuck’s centerline to the desired radius.
Heating and Bending: Insert the pipe into the heating coil, adjust the gap, heat to 950–1000°C, start motor to bend, and spray water to cool.
Cooling and Inspection: Stop heating and motor at the desired angle, continue cooling to room temperature, remove the pipe bend, and check quality.
Pipe bends are widely used across various industries. The following are some common application examples.
In ship piping systems, pipe bends are used to connect equipment and pipelines at different positions, ensuring smooth flow of liquids and gases. Ship pipelines often need to withstand high pressure and corrosive environments, so stainless steel bends or cast iron bends are commonly used.
In automotive piping systems, pipe bends connect components such as the engine, cooling system, and fuel system. Automotive pipes require good pressure resistance and corrosion resistance while maintaining lightweight construction. Therefore, aluminum alloy bends or stainless steel bends are commonly employed.
In building water supply and drainage systems, pipe bends connect vertical and horizontal pipelines to ensure smooth water flow. These bends need excellent corrosion resistance and sealing performance, so cast iron bends or PVC bends are often used.
In chemical piping systems, pipe bends transport various chemical substances and must have strong corrosion and pressure resistance. Stainless steel bends or fiberglass-reinforced bends are commonly used to meet the requirements of different chemical media.
Pipe bends are a critical component of pipeline systems, and their manufacturing and maintenance significantly impact the performance and service life of the system. By understanding the types of pipe bends, their manufacturing processes, maintenance methods, and associated equipment, you can better select and use bends to ensure the safe and efficient operation of your pipeline system. We hope this article has been helpful. For any further questions or additional information, please feel free to contact us.
